Techniques for granulating and coating are known including granulating and coating various powder and granules such as medicines, foods, synthetic chemical products, etc. by supplying and discharging gas such as hot air blown into and from a rotary drum (coating pan) while rotating the rotary drum around a horizontal axis.
In the technique described above, there is raised a technical problem of how to agitate and mix the powder and granules efficiently in the rotary drum in order to accomplish a desired granulating or coating operation efficiently and homogeneously. To solve this problem, it has been proposed to provide a baffle device fixed in the rotary drum for functioning as an obstacle to the flow of the granules etc. (See Japanese Patent No. Sho 52-10665 Gazette). For the baffle device, there is proposed a baffle device in which its position is movable along with an axis or between the inside and outside of the granular layer.
In the former prior art described above, however, there is seen a phenomenon that the raw material of the powder and granules tends to adhere to the baffle device when processing of granulation and coating is carried out, then the material adhered is peeled off therefrom into the rotary drum, because the baffle device is installed on a fixed position. In such phenomenon, the adhered material detaches from the baffle device, then it can be a cause of defects such as unevenness in the thickness of the coated layer, oversized products so-called double tablets and irregular-shaped products which are a result of the adhesion of the material peeled off to the granulated products.
The later prior art described above provides an improved agitating operation accomplished by using the baffle device, however, the inventors herein found that it cannot solve all of the problems as described above and has defects due to the adhesion of powder and granules to the baffle device and the inner wall of the rotary drum and their peeling off therefrom as well.